Numerous secondary plant constituents inhibit the growth and development of other organisms. Constitutive and induced compounds protect the donor plant from stress imposed by insects, fungi, herbivores, and competing plants, [Bailey et al., Phytoalexins, 1982, New York; Rice, Allelopathy, 1984, Academic, Florida; Powell et al., ACS Symp. Ser. 380, 1988, pages 211-232]. Saturated pyrrolizidine alkaloids of the loline type occur in relatively high concentrations in tall fescue that is infected with Acremonium coenophialum [Petroski et al., J. Nat. Prod. 52: 810-817 (1989)], but they have not been detected in tall fescue in the absence of this fungus. The lolines have not been considered contributors to the observed allelopathy of tall fescue [Peters, Crop Sci. 8: 650-653 (1968); Peters et al., Agron. J. 73(1): 56-58 (1981); Walters et al., J. Chem. Ecol. 2: 469-479 (1976)].
The plant kingdom uses chemical substances as defenses against insects [Jacobson, Econ. Bot. 36: 346-354 (1981)]. A recent report which outlined one such plant-insect relationship [Johnson et al., Appl. Environ. Microbiol. 49: 568-571 (1985)] indicated that tall fescue plants infected with an endophytic fungus produced compounds which deter feeding aphids and milkweed bugs. In an effort to identify the compounds which were active in deterring feeding, these authors prepared extracts of tissue from endophyte-infected plants. Because the extracts contained a mixture of alkaloid types, active compounds were not specifically identified.
Using extracts from seeds of endophyte-infected plants, Yates et al. [J. Agric. Food Chem. 37: 354-357 (1989)] showed that N-formylloline and related alkaloids were potent toxins to milkweed bugs. Further fractionation of the extracts revealed the presence of several derivatives of loline, namely N-methylloline and N-acetylloline, as well as N-formylloline [Yates et al., J. Agric. Food Chem. 38: 182-195 (1990)].